Automatic identification (“Auto-ID”) technology is used to help machines identify objects and capture data automatically. One of the earliest Auto-ID technologies was the bar code, which uses an alternating series of thin and wide bands that can be digitally interpreted by an optical scanner. This technology gained widespread adoption and near-universal acceptance with the designation of the Universal Product Code (“UPC”)—a standard governed by an industry-wide consortium called the Uniform Code Council. Formally adopted in 1973, the UPC is one of the most ubiquitous symbols present on virtually all manufactured goods today and has allowed for enormous efficiency in the tracking of goods through the manufacturing, supply, and distribution of various goods.
However, the bar code still requires manual interrogation by a human operator to scan each tagged object individually with a scanner. This is a line-of-sight process that has inherent limitations in speed and reliability. In addition, the UPC bar codes only allow for manufacturer and product type information to be encoded into the barcode, not the unique item's serial number. The bar code on one milk carton is the same as every other, making it impossible to count objects or individually check expiration dates, much less find one particular carton of many.
Currently, retail items are marked with barcode labels. These printed labels have over 40 “standard” layouts, can be mis-printed, smeared, mis-positioned and mis-labeled. In transit, these outer labels are often damaged or lost. Upon receipt, the pallets typically have to be broken-down and each case scanned into an enterprise system. Error rates at each point in the supply chain have been 4-18% thus creating a billion dollar inventory visibility problem. However, Radio Frequency Identification (RFID) allows the physical layer of actual goods to automatically be tied into software applications, to provide accurate tracking.
The emerging RFID technology employs a Radio Frequency (RF) wireless link and ultra-small embedded computer chips, to overcome these barcode limitations. RFID technology allows physical objects to be identified and tracked via these wireless “tags”. It functions like a bar code that communicates to the reader automatically without needing manual line-of-sight scanning or singulation of the objects.
Current methods of tracking RFID tagged objects rely on triangulation of a tag's signal using multiple readers. However, triangulation typically provides only a general vicinity of the tagged item. If the user wants to physically retrieve the tagged item, the user must still manually search for the tagged item in that general area. This can be a very time consuming process in a large venue with potentially hundreds or thousands of tagged items within a few feet of each other.
Further, because RF energy is reflected by other objects in the environment, environmental reflections of the tag's signal can skew the triangulation result, causing the system to indicate the wrong general location of the tag.
A further drawback of triangulation is that all tags are activated and singulated until the desired tag is found. In a warehouse for example, where there may be tens of thousands of tags, the singulation process may take a long time; meanwhile precious battery power is being consumed on those tags waiting to be singulated and respond.
What are therefore needed are new and more efficient methods and systems to track and singulate homogeneous and/or nonhomogeneous tagged items.